1. Field of the Invention
The present invention relates to a photosensitive member comprising an overcoat layer on a monolayer construction of selenium-arsenic alloy or a laminate-layer construction of selenium-tellurium alloy.
2. Description of the Prior Art
Photosensitive members of amorphous selenium have been well known, and there have been many attempts to improve the disadvantages in heat resistance, spectral sensitivity, dark decay and the like of such members. For example, arsenic is doped into a selenium layer, or selenium-tellurium alloy layer is formed on a selenium layer to obtain a photosensitive member of laminated structure.
It has conventionally been well known that photosensitive members composed of selenium-arsenic alloys (hereinafter referred to as Se-As) have the highest photosensitivity in spectral luminous efficiency of all the members and that members comprising a selenium layer having a selenium-tellurium layer (hereinafter referred to as Se-Te) laminated thereon has the highest sensitivity in long wavelength light which is required for a printer using semiconducting laser beams as a light source.
However, conventional Se-As and Se-Te photosensitive members in common use have the following disadvantages. One disadvantage is that they are harmful to the human body. Although it is nearly impossible for the photosensitive member to come into direct contact with the human body, when such a photosensitive member is used in a copy machine, powder from said member adheres to the copy image due to surface friction caused by the member rubbing against the copy paper, cleaning materials, developer or other matter, and the powder is then discharged from the machine. Accordingly, when the copy is picked up by hand the person is directly contaminated by the selenium, arsenic and tellurium, the harmfulness of said substances being a matter for concern. Another disadvantage is poor durability. The surface hardness of Se-As and Se-Te photosensitive members barely meets the H level of the JIS standards for pencil lead hardness, consequently, the surface is readily damaged when friction is generated during use of the machine as described previously, or repeated harsh surface contact is made during paper jams and the resultant reversion to manual remedies. This damage markedly reduces the image quality due to so-called whiteouts on the copy image, and shortens the useful life span of the photosensitive material.
In order to eliminate these disadvantages, the surface of the Se-As or Se-Te photosensitive member is covered with a protective layer.
For example, Japanese Unexamined Patent Publications Nos. SHO 53-23636 and SHO 53-111734 disclose photosensitive members having a specific silicide applied on a selenium, selenium-tellurium alloy, and selenium-cadmium alloy photoconductive layers and hardened to form an insulating layer. Japanese Unexamined Patent Publication No. SHO 59-58437 discloses a photosensitive member having an amorphous Si:N or Si:O layer of 50 angstroms to 2 microns in thickness formed on a selenium-arsenic alloy layer by the glow discharge process using silane gas and ammonia gas, or silane gas and nitrous oxide gas as starting materials. Japanese Unexamined Patent Publication No. SHO 60-61761 discloses a photosensitive member having an amorphous carbon or hard carbon layer formed on a photosensitive layer. Japanese Unexamined Patent Publication No. SHO 62-9355 discloses a photosensitive member having an overcoat layer of amorphous carbon formed on the surface of a photo-exciting layer comprising hydrogenated/halogenated amorphous carbon or hydrogenated amorphous silicon.
However, photosensitive members disclosed in Japanese Unexamined Patent Publications No. SHO 53-23636 and 53-111734 have a drawback that the surface of the members are readily damaged due to its poor surface hardness. Photosensitive members disclosed in Japanese Unexamined Patent Publications No. SHO 59-58437, 60-61761 and 62-9355 produce so-called image drift under conditions of high temperature and humidity. Particularly, Japanese Unexamined Patent Publication No. 60-61761 discloses a photoconductive layer of amorphous silicon. Therefore, when this technique is applied to the members composed of selenium, there arises a problem of reduced chargeability.
As apparent from the above, there is no disclosure in these publications of any means for resolving the basic disadvantages inherent in the aforementioned Se-As and Se-Te photosensitive members.